With development of electronic paper display technology, display devices based on electronic paper technology advance in the direction of bright colors, ultra thinness and energy saving.
A display device of electronic paper type generally comprises an upper substrate (such as a silica gel film or glass substrate) and a lower substrate (such as a silica gel film or glass substrate), and a liquid crystal layer or a microsphere layer; the upper substrate comprises common electrodes, while the lower substrate comprises thin film transistors (TFTs), pixel electrodes and a reflective layer; and the pixel electrodes generate variable electric field between the upper substrate and the lower substrate according to the signals received by the TFTs, and liquid crystals of the liquid crystal layer or microspheres of the microsphere layer are changed by the change of the electric field, such that the display device displays images.
Most of electronic paper technologies in the current technologies are based on white and black ink microspheres, and such electronic paper display device utilizes a transparent film similar to a piece of common paper, and charged microspheres with a size of about 100 microns and in an amount up to millions are distributed within the film. The microspheres have a shape of round sphere, and an end of one microsphere is coated with positively charged black coating, and the other end of the microsphere is coated with negatively charged white coating. The microspheres are sealed in a transparent silica gel film filled with lubricant oil. Circuits similar to thin film transistors in a liquid crystal display are configured on one surface of the silica film, and can apply a positive voltage or a negative voltage at various positions according to actual requirements. These charged microspheres immersed in the lubricant oil will rotate under the effect of an electric field. White portions or black portions are selectively turned out, and texts or images needed to be displayed can be formed in a macro-scale. However, such electric paper display device can only display black and white images and cannot achieve color display.
There has been provided an electric paper color display device in the current technologies. However, such display device is based on positively or negatively charged color ink microspheres with a shape of round sphere, and color ink microspheres need to be coated with coating of various colors. As images are displayed only with colors that the color ink microspheres have by themselves, there are some problems in such a display device, such as flat display colors, poor display effect, long response time, expensive price, and etc. Moreover, a color display device based on liquid crystal needs a color filter, loss of light will occur, and light transmittance will be reduced. Thus, an additional light source will be required to provide illumination and additional electric energy will be consumed. Furthermore, colors of images based on color filters are not simply structured light generated by reflection, and the color effect is poor and the contrast is low.